1. Field of the Invention
The present invention relates to a layered body of mounting a SAW filter, a high frequency switch, and a radio communication apparatus, which are used for a mobile phone and so on, for example.
2. Related Art of the Invention
In recent years, in view of the increasing number of users of mobile communication and globalization of a system, for example, high frequency switches have received attention. The high frequency switches are provided for using systems of EGSM (Enhanced-Global System for Mobile Communication) DCS (Digital Cellular System), and PCS (Personal Communications Services), which have corresponding frequency bands of FIG. 7, in a single mobile phone and so on. Besides, FIG. 7 is an explanatory drawing showing the corresponding frequency bands of EGSM, DCS, and PCS.
Referring now to FIG. 8, which is a block diagram showing a conventional high frequency switch, the following will discuss the configuration and operation of the conventional high frequency switch used for a mobile phone and so on.
A conventional high frequency switch 800 is provided for triple bands (the above-mentioned EGSM, DCS, and PCS) that comprises transmit-receive switch circuits 801 and 802, a branching filter circuit 803 for connecting the transmit-receive switch circuits 801 and 802 to an antenna (ANT), and low-pass filters 804 and 805 of suppressing high-frequency distortion during transmission. Further, band-pass filters 806, 807, and 808 are connected to a receiving end to extract only a desired frequency band, and a packaged SAW filter is mainly used as a band-pass filter.
The conventional high-frequency switch 800 generally uses PIN diodes as the transmit-receive switch circuits 801 and 802. Inductors and capacitors constituting the transmit-receive switch circuits 801 and 802, the branching filter circuit 803, the low-pass filters 804 and 805 are formed as internal layers serving as electrode patterns in a layered body or a remounted on a surface layer by using chip components. Thus, the branching filter circuit 803, the transmit receive switch circuits 801 and 802, and the low-pass filters 804 and 805 are realized as a single lamination device.
However, a SAW filter and the high-frequency switch 800 on a receiving end need to be connected on a main substrate. On this account, it is necessary to obtain a sufficiently wide packaging area, so that it is difficult to miniaturize mobile phones.
Further, it is considered that a conventionally packaged SAW filter is mounted on a surface layer of the high-frequency switch 800. However, since a packaged SAW filter has a large size of about 3 mm square and has a height of about 1 mm, it has been difficult to achieve a small and low high-frequency switch.
Moreover, it is considered that a SAW filter such as a bare chip is mounted on a surface layer. However, in this case, it is necessary to obtain grounding strength as that of a conventional package of a SAW filter, and a balance characteristic deteriorates. Thus, it has been difficult to realize such a configuration.
In view of the above-described problems, in order to mount a SAW filter on a surface layer of a high-frequency switch and to achieve a low-profile device, the present invention has as its object the provision of small and low-profile layered body of mounting a SAW filter, high-frequency switch, and radio communication apparatus whereby grounding strength can be sufficiently obtained in the high-frequency switch to a degree which has been conventionally obtained in a package, and preferred characteristics are achieved without deterioration in balance characteristic.
One aspect of the present invention is a layered body of mounting at least one SAW filter comprising:
a surface dielectric layer having a surface layer electrode pattern formed thereon, and
a first dielectric layer having a pair of electrode patterns and a first ground electrode pattern formed thereon,
wherein a pair of balanced output terminals of the SAW filter of unbalanced input-balanced output are to be connected respectively to the pair of electrode patterns via the surface layer electrode pattern, and
a part of the first ground electrode pattern is disposed between the pair of the electrode patterns.
Another aspect of the present invention is a layered body of mounting at least one SAW filter comprising:
a surface dielectric layer having a surface layer electrode pattern formed thereon, and
a first dielectric layer having a pair of electrode patterns and a first ground electrode pattern formed thereon,
wherein a pair of balanced output terminals of the SAW filter of unbalanced input-balanced output are to be connected respectively to the pair of electrode patterns via the surface layer electrode pattern, and
a part of the first ground electrode pattern is disposed on both sides of the pair of electrode patterns.
Still another aspect of the present invention is a high-frequency switch having a plurality of signal paths corresponding to a plurality of frequency bands,
the high-frequency switch, comprising:
a branching filter circuit which combines transmitted signals from the plurality of signal paths during transmission and distributes received signals to the plurality of signal paths during reception,
a plurality of transmit-receive switch circuits of switching the plurality of signal paths to a transmitting part and a receiving part, and
a plurality of filters disposed in the signal paths,
wherein at least one of a strip line and a capacitor which constitute the branching filter circuit, the plurality of transmit-receive switch circuits, and the plurality of filters is formed as an electrode in a layered body,
at least one of the plurality of filters is constituted by the SAW filter,
the SAW filter is mounted on a surface of the layered body, and
the layered body is a layered body of mounting a SAW filter.
Yet still another aspect of the present invention is the high-frequency switch, further comprising one or more second ground electrode patterns in the layered body.
wherein the first dielectric layer is disposed directly under a surface layer of a dielectric layer formed on the surface layer of the layered body, and
the first ground electrode pattern is electrically connected to the second ground electrode pattern formed on a back of a first external terminal electrode disposed on a lowest surface of the layered body or to a third ground electrode pattern formed between the first ground electrode pattern and the second ground electrode pattern through a first via hole electrode.
Still yet another aspect of the present invention is the high-frequency switch, wherein the first via hole electrode of electrically connecting the first ground electrode pattern and the second ground electrode pattern is disposed at least on each corner of the first ground electrode pattern.
A further aspect of the present invention is the high-frequency switch, wherein the first via hole electrode is larger in diameter than a second via hole electrode of connecting the strip line and the capacitor electrode which constitute the branching filter circuit, the plurality of transmit-receive switch circuits, and the plurality of filters.
A still further aspect of the present invention is the high-frequency switch, wherein of the strip lines and the capacitor electrode which constitute the branching filter circuit, the plurality of transmit-receive switch circuits, and the plurality of filters, an electrode pattern formed in the layered body is disposed on a dielectric layer between the first ground electrode and the second ground electrode.
A yet further aspect of the present invention is the high-frequency switch, wherein the surface electrode pattern has a first surface layer electrode pattern electrically connected to a ground electrode terminal of the SAW filter, an
the first ground electrode pattern is electrically connected to the first surface layer electrode pattern through the first via hole electrode.
A still yet further aspect of the present invention is the high-frequency switch, wherein the first ground electrode pattern is partially connected to the second or third ground electrode pattern through the first via hole electrode.
An additional aspect of the present invention is a radio communication apparatus, comprising:
a high-frequency switch,
a transmitting circuit of outputting a transmitted signal to the high-frequency switch, and
a receiving circuit of inputting a received signal from the high-frequency switch.